Such an agreement could give Slack a valuation of $9 billion.
However, a takeover isn't assured and discussions on such a deal may take longer, according to reports.
Slack is yet to respond to the report.
Amazon eyeing bid for corporate messaging platform Slack
Slack turns its eye to bigger users
Slack was founded in August 2013 as business chat software by Stewart Butterfield.
Slack is an acronym that stands for 'Searchable Log of All Conversation and Knowledge'.
In Jan'17, Slacked introduced the enterprise version of its chat platform, allowing thousands of employees to collaborate across major corporations.
It has 5 million daily active users, of whom 1.5 million are paid users.
Silicon Valley giants notice Slack's massive expansion
The corporate messaging platform has come a long way since its inception; from a gaming company's side project to becoming a giant in the productivity software sector.
After raising $200mn in its last funding round in 2016, it was valued at $3.8bn.
To compete with Slack, Microsoft rolled out its own corporate chat platform called 'Teams' in Mar'17.
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Google, Facebook also compete with Slack
In Oct'16, Facebook started its own collaborative platform called 'WorkPlace' and offered a three-month free trial, gunning for rival Slack.
Over 1,000 companies had signed up to use it.
In Mar'17, Google announced a revamped version of Hangouts and split it into Meet and Chat, challenging Slack.
Hangouts Chat is a team messaging service for offices available on mobile and desktop.
Slack is available on mobile platforms like iOS, Android and Windows Phone (beta) as well as on web and desktop platforms like Windows, macOS, and Linux (beta). It is also available for Apple Watch, which allows users to see mentions and send direct messages.